Prehistoric fires and land-cover change in western Kenya: evidences from pollen, charcoal, grass cuticles and grass phytoliths

Abstract

High rates of sediment accumulation in Lake Simbi, western Kenya, has enabled fine-resolution fossil assemblages to reveal short-term changes in vegetation cover between 4320 ± 250 yr BP and 2880 ± 90 yr BP. Pollen analysis of a 4.2 sediment core covering this period reveals a vegetation change around 3300 yr BP. Analysis of charcoal shows that wildfires were prominent prior to the pollen-inferred vegetation change. Remains of grass cuticles and grass phytoliths show an expansion of grasslands and an increase in the diversity of grass types following the period of extensive fires. Also following the period of wildfires and the vegetation change, there were shifts within the grass flora to more Chloridoid grass types and less Panicoid grass types. This paper addresses one of the major problems of environmental reconstruction in lowland savannah: namely differentiating palaeoecological changes within the Gramineae.